Black tea, is my secret weapon.
Trick is to pour only boiling water on the tea bag. hot water does not release the tanins and flavonoids, it must be boiling water.
I drink about 3 large cups, 24oz size before tennis, and in fact drink about 6 cups of this per day. It really seems to raise your game, and at the same time, does not get you completely jolted up on cafreine like coffe, much easirer on your body.
I also think it improves your cadiovascular health, by removing plaques from the arteries, while coffe actually can contribute to heart disease. Black tea, is better than green tea, in my view.